FIG. 10.—Different aspects of sections of the spinal cord and of the roots of the spinal nerves
from the cervical region: 1, different views of anterior median fissure; 2, posterior fissure; 3,
anterior lateral depression for anterior roots; 4, posterior lateral depression for posterior roots;
5 and 6, anterior and posterior roots, respectively; 7, complete spinal nerve, formed by the
union of the anterior and posterior roots.The Spinal Cord.—The spinal cord proceeds from the base of the brain
downward about eighteen inches through a canal provided for it in the vertebræ
of the spinal column. It is composed of white matter on the outside, and gray
matter within. A deep fissure on the anterior side and another on the posterior
cleave the cord nearly in twain, resembling the brain in this particular. The gray
matter on the interior is in the form of two crescents connected by a narrow bar.
The peripheral nervous system consists of thirty-one pairs of nerves, with their
end-organs, branching off from the cord, and twelve pairs that have their roots in
the brain. Branches of these forty-three pairs of nerves reach to every part of the
periphery of the body and to all the internal organs.